wasd greyhounds What's needed is an intermodal system that can use lower cost terminals and that just ain't double stack. I'd suggest a psedo TOFC circus loading operation using containers on chassis for serving places such as Storm Lake. https://youtu.be/MTvSOrTXFzw There. Solved your problem. These train sets can be loaded and unloaded in half an hour and can carry any trailer without the need for craneable trailers or any other special equipment. I can already think of a few corridors. Montreal-Toronto sticks out most in my mind. This essentially solves short-haul intermodal and does what roadrailers could never do.
greyhounds What's needed is an intermodal system that can use lower cost terminals and that just ain't double stack. I'd suggest a psedo TOFC circus loading operation using containers on chassis for serving places such as Storm Lake.
https://youtu.be/MTvSOrTXFzw
There. Solved your problem. These train sets can be loaded and unloaded in half an hour and can carry any trailer without the need for craneable trailers or any other special equipment.
I can already think of a few corridors. Montreal-Toronto sticks out most in my mind. This essentially solves short-haul intermodal and does what roadrailers could never do.
While the LOHR system has it attributes it’s still more expensive to operate than CP’s former Expressway service. Which is the best solution to short haul IM domestically.
SD60MAC9500While the LOHR system has it attributes it’s still more expensive to operate than CP’s former Expressway service. Which is the best solution to short haul IM domestically.
Didn't Expressway take ages to load/unload? Technology is not as important though. Short haul TOFC is the next frontier for railroads. They need to learn lessons from Europe to make it work.
Learn from Europe (or anywhere else)? Given the management, that's unlikely.
wasd SD60MAC9500 While the LOHR system has it attributes it’s still more expensive to operate than CP’s former Expressway service. Which is the best solution to short haul IM domestically. Didn't Expressway take ages to load/unload? Technology is not as important though. Short haul TOFC is the next frontier for railroads. They need to learn lessons from Europe to make it work.
SD60MAC9500 While the LOHR system has it attributes it’s still more expensive to operate than CP’s former Expressway service. Which is the best solution to short haul IM domestically.
Approx. 90 mins to load/unload Expressway trains. One thing you have to remember. The Euro operators don't own the RoW so they can be more flexible on cost. Two different operating theaters which require different solutions. So what works in Europe will not always work over here and vice versa..
bogie_engineer It made it unattractive to develop new and better devices, rather only cheaper versions of the same old thing, which is why we are still using the 3 piece truck in spite of it's well known deficiencies. Dave
It made it unattractive to develop new and better devices, rather only cheaper versions of the same old thing, which is why we are still using the 3 piece truck in spite of it's well known deficiencies.
Dave
Speaking of bogies. Check this one out.
https://news.cision.com/skf/r/skf-collaborates-with-ats-to-develop-solutions-to-reduce-life-cycle-cost-for-rail-freight,c2774160
http://advancedtrucksystems.com/
wasdDidn't Expressway take ages to load/unload?
Any circus-type arrangement that does not carry its own power inherently does. Dividing a train into rakes lowers this, but not always 'net' of switching and tie-down time and cost. Trailers must be precisely backed down, then parked and the tractor extracted before the kingpin hitch can be raised and adjusted; on arrival the special hydraulic-lift yard tractors have to back in and bind on sequentially.
The specialized Expressway flats have fixed side rails, which is nifty for train ferries or Braille backing-down but not great for side access or turning by yard tractors (see Flexi-Van) which would allow gang unloading easily -- the more important time constraint. Personally, I don't think any system that relies on specialized driver skill is likely to have higher take rate over one that is drop-hook with experienced 'yard' tractor crews with specialized equipment. That will likely persist into a more autonomous age, where specialized equipment to gang-access vans won't be at all what suits long-distance, and designing machines to do both well -- while certainly possible -- will be no more successful than RailRunners.
greyhounds charlie hebdo Interesting views but I think jbs1 might enlighten us better on cost accounting. Several of your comments suggest your knowledge of proper accounting is not very thorough. OK, just what comments are you talking about? Or are you following your ususal path of just making stuff up to slam other people.
charlie hebdo Interesting views but I think jbs1 might enlighten us better on cost accounting. Several of your comments suggest your knowledge of proper accounting is not very thorough.
OK, just what comments are you talking about? Or are you following your ususal path of just making stuff up to slam other people.
I thought most of your post was very informative. But your remark was that cost accounting in railroading is garbage. That seems like name-calling of the worst sort although it is clear that some on here despise accountancy (and statistics and finance) out of ignorance Or is any criticism of your posts regarded as an insult? Get a thicker skin.
rdamonIt would be interesting to see if they could incorporate a commuter like platform where there is close enough clearance to facilitate a right or left turn off the flat car on to the platform.
The platforms can indeed be angled like ramps close to the line of the track. For CargoSpeed this would be limited by the high-centering clearance of the angled trailers, between bogie and landing gear, when set down, and by the slow-speed power and tractive effort of the tractors used for loading/unloading. I confess that my preference has always been for level platforming continuous on either side of the line of the track for the angled approaches. If ganged loading and loading don't need to be combined, the apron on the 'far' side can be far less wide (as it need only accommodate slight bogie-tire contact as vehicles are positioned over the flat, the tractors drop and reposition, and swing the trailer nose parallel).
In my opinion it should be possible to set up HA-NDGPS such that backing precision relative to the train can be precise no matter where adjustable trailer bogies have been set, and assurance made that when the nose is swung the kingpin will be where the hitch will rise; a good yard tractor will be able to slew the hydraulic fifth wheel laterally as well as lift, so very fine positioning of the trailer longitudinally, rather than tinkering with or expensively powering the hitch locations, is simplified.
Many of the steps in effective TOFC loading/unloading time reduction involve a critical path, and detail attention to reducing the time of the items affecting this is wise; conversely money can be saved by not demanding rocket speed or fancy robotics on what turn out to be less critical functions.
My assumption many years ago was that reducing dwell time of the trainset was the principal concern, and that (as with the container sideloading) subsequent actions for road departure could involve multiple less time-critical (and potentially asynchronized) steps. For example, CargoSpeed as originally designed used the on-road tractors to pull the trailers across the cars to loading position, and then similar tractors to bind on to the angled unloaded trailers for prompt road departure. In my opinion it makes better sense to use dedicated yard equipment, either with skilled (and unionized) local drivers or highly optimized autonomous control, to perform the actual intermodal part, and then stage appropriately (perhaps in disparate parts of the facility or even at some distance from it) to where the actual road-optimized tractors or bogies for road trains will be assembled.
Some here have commented about the increase aerodynamic drag of double stacks. Is it really an issue. Do most stack trains operate continuously at a speed where it becomes more important than the less mechanical drag due to fewer wheelsets, etc.?
There's a variety of answers to this.
In most current practice, in a scheduled intermodal paradigm that values timely more than fast delivery, with railroads obsessed with notch 5 or 6 restrictions, most of the aerodynamic-drag issues are comparatively minor -- in other words, the cost to address them is more than the added fuel or power they induce.
On the other hand, under certain conditions (e.g. strong prevailing winds 'quartering' to the train direction) the aerodynamic resistance can become appalling. If I recall correctly this was one of the major concerns around dropping trailers riding on spine cars into 'kangaroo pockets' on ATSF. Here the 'solution' will involve just how much emphasis the responsible bean counters place on the fractional-mpg improvements 'better earo' might provide -- as you know, many times a savings of less that 1/10 a unit becomes significant with sufficient volume and time.
Some railroads still have higher operating speed (UP being last I looked an example) and these can fall prey to knotheaded ideas like Arrowedge. If there was a measurable gain from either iteration of that silliness I've been unable to calculate it reliably, even before you get into the terrifying naivete in actual aerodynamics that led to crumpling under bridges. There is a very long history of the practical effect of streamlining on high-speed trains, with the Metroliner testing being an interesting example of what works and what doesn't: almost all the resistance is not at the head end of any train, but in the 'interstices', and this is where the spacing of containers in typical articulated well trains produces the effect.
There is also the equipment utilixzation 'cost' to consider here. Stack allows the same set to operate at roughly half the speed of a more 'aerodynamic' alternative, for less than proportional tare -- this can make up a great deal of perceived 'opportunity cost' for cheaper speed, and also facilitate more fluid one-speed operation at economical throttle settings for modern power.
Note that where UPS has tried accelerating Z trains, the additional service hasn't paid, net of any attempts made at drag reduction. That's depressing to me, but I have little if any reason to second-guess their work.
What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8.
I thought this was a factor in preferring an SD-40 over and SD-45 -- for a given tech for wheel slip control requiring a given number of axles to crest the ruling grade, there is a HP/per axle that allows operating in Notch 8 more of the time for better fuel economy?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Railroads are so bent on saving every drop of fuel they can, locomotive engineers are prohibited from going over Notch 5 or 6 or 7 on their consist. I've had many trains where I may have 2 or 3 engines but I am only allowed to use notch 5 or 6 on two of them, heck many times I am only allowed to use 5 or 6 or 7 on one!
Unless I am going downhill, there are many trains I have that may never see 40 mph because the power restrictions are so severe. Low 30's may be where I spend the majority of the trip.
Heck, we're not allowed to use Trip Optimizer because it burns more fuel than they're okay with.
This is on all trains. Even the higher priority intermodal trains that have 1.0 hpt really aren't fast because they're so long, the drag slows you down. The green lights are the only thing that allow you to keep pace.
The carriers no longer care about speed. It's all about cutting costs.
10000 feet and no dynamics? Today is going to be a good day ...
Paul MilenkovicI had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8.
Even in Trains back in the day (when they were discussinf Perlman at WP, which dates it) it was pointed out that two '40s in Run 8 burned more fuel than three in a lower notch making equivalent dbhp. That would not have changed with improved injection control or better chamber design, etc.
The argument about running trains 'too slow' for best cumulative fuel efficiency is subtlely different, and has been covered by a couple of posters with direct experience. Even so, I expect there will be a 'company notch' for each type of power at which the engine and drive systems produce the equivalent of 'cruise' sfc in aircraft == and it won't be at the equivalent of full military power on most designs.
Overmod Paul Milenkovic I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8. Where? Even in Trains back in the day (when they were discussinf Perlman at WP, which dates it) it was pointed out that two '40s in Run 8 burned more fuel than three in a lower notch making equivalent dbhp. That would not have changed with improved injection control or better chamber design, etc. The argument about running trains 'too slow' for best cumulative fuel efficiency is subtlely different, and has been covered by a couple of posters with direct experience. Even so, I expect there will be a 'company notch' for each type of power at which the engine and drive systems produce the equivalent of 'cruise' sfc in aircraft == and it won't be at the equivalent of full military power on most designs.
Paul Milenkovic I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8.
Where?
When tool for fuel saving is specified maximum Mile Per Hour it can waste fuel in some territories.
The CSX line from Atlanta to Waycross undulates across the rolling landscape that is the territory between the two point. In the early 90's CSX specified 40 MPH as the Maximum Speed for Coal Trains in the name of 'Fuel Conservation'. After several months of compliance and having a number of trains stall in locations that they had never stalled before - The Senior Road Foreman of Engines got the higher ups to listen to his theory - braking the trains to 40 MPH on the downside of the rolling terrain left them with insufficient kinetic energy to climb the resulting upgrade of the next hill - trains were in Run 8 longer at 40 MPH than they had been before the Fuel Conservation restriction.
Later a comparison test was done - two coal trains of similar tonnage and power. At the time 90 cars was the standard coal train and the standard power was two GE Dash-8's. Fuel levels were noted at Atlanta and then at Waycross. The train that WAS NOT observing 'Fuel Conservation' use about 150 gallons less per unit than did the train that observed 'Fuel Conservation'. After the test coal train were no longer restricted to 40 MPH on that territory in the name of Fuel Conservation.
Never too old to have a happy childhood!
The same moron idea that enforced speed limits save fuel.
Even in the '70s the speed limit would better have been "100kph" (=62.5mph) which was where many trucks had good cruising performance. It is also very well recognized that over-the-road economy may involve going relatively slowly uphill and getting ungoverned gravity-assist speed going down -- Shadow's owner will probably be able to describe support for this operating 'paradigm' although I, as a driver trying to run on cruise control at constant speed, am repeatedly annoyed at the passing pas de deux that is required to cope with it.
The common-sense version of 'restricted speed to save fuel' is 'restricted throttle notch' -- let the balancing speed work out how it may, up to permissible track speed. Even I appreciate this.
traisessive1 Railroads are so bent on saving every drop of fuel they can, locomotive engineers are prohibited from going over Notch 5 or 6 or 7 on their consist. I've had many trains where I may have 2 or 3 engines but I am only allowed to use notch 5 or 6 on two of them, heck many times I am only allowed to use 5 or 6 or 7 on one! Unless I am going downhill, there are many trains I have that may never see 40 mph because the power restrictions are so severe. Low 30's may be where I spend the majority of the trip. Heck, we're not allowed to use Trip Optimizer because it burns more fuel than they're okay with. This is on all trains. Even the higher priority intermodal trains that have 1.0 hpt really aren't fast because they're so long, the drag slows you down. The green lights are the only thing that allow you to keep pace. The carriers no longer care about speed. It's all about cutting costs.
I wish we didn't have to use Trip Optimizer.
Our fuel conservation speed is 50 mph. You can't exceed notch 6 above 50 mph without authority. During the intermodal "rush" season, the hottest Z trains are instructed to have everything on line (up to powered axle limits) and the FCS (fuel conservation speed) is voided.
Jeff
Paul Milenkovic What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8.
It was explained to me that the railroad figures it's getting it's most value out of fuel in notch 8. The manager (who was himself not sure of this claim) figured they were thinking of a locomotive on a coal train pulling it's guts out at 10 - 15 mph as it struggles over a hill. Not so much of a hot shot in notch 8 at 70 mph.
A chart for the 16-710G3 shows ~ 0.405lb/hp-hr in notch 2, ~0.360lb/hp-hr in notch 3, just under 0.350lb/hp-hr in notch 4, 5 & 6, a minimum of ~0.330lb/hp-hr in notch 7 and a bit higher in notch 8. Looks like you want to run in notch 7 or 8 as much as possible, idling some units when full power isn't needed.
Erik_Mag Paul Milenkovic What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8. A chart for the 16-710G3 shows ~ 0.405lb/hp-hr in notch 2, ~0.360lb/hp-hr in notch 3, just under 0.350lb/hp-hr in notch 4, 5 & 6, a minimum of ~0.330lb/hp-hr in notch 7 and a bit higher in notch 8. Looks like you want to run in notch 7 or 8 as much as possible, idling some units when full power isn't needed.
Peter might know something about this. National Rail in Australia has a fleet of variable horsepower locomotives (NR Class, I think) that can adjust HP to fit the trailing tonnage and conserve fuel.
rdamon Erik_Mag Paul Milenkovic What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8. A chart for the 16-710G3 shows ~ 0.405lb/hp-hr in notch 2, ~0.360lb/hp-hr in notch 3, just under 0.350lb/hp-hr in notch 4, 5 & 6, a minimum of ~0.330lb/hp-hr in notch 7 and a bit higher in notch 8. Looks like you want to run in notch 7 or 8 as much as possible, idling some units when full power isn't needed. Would this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint?
The complaint against Genset's was the took so long to fire up the additional HP and get it loading that the move had stalled by the time the additional power was available for use.
BaltACD rdamon Erik_Mag Paul Milenkovic What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8. A chart for the 16-710G3 shows ~ 0.405lb/hp-hr in notch 2, ~0.360lb/hp-hr in notch 3, just under 0.350lb/hp-hr in notch 4, 5 & 6, a minimum of ~0.330lb/hp-hr in notch 7 and a bit higher in notch 8. Looks like you want to run in notch 7 or 8 as much as possible, idling some units when full power isn't needed. Would this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint? The complaint against Genset's was the took so long to fire up the additional HP and get it loading that the move had stalled by the time the additional power was available for use.
I see that issue for gen-set use in switching applications. In road use where changes are less abrupt, and terrain is known this seems like it could be more automated and planned.
rdamon BaltACD rdamon Erik_Mag Paul Milenkovic What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8. A chart for the 16-710G3 shows ~ 0.405lb/hp-hr in notch 2, ~0.360lb/hp-hr in notch 3, just under 0.350lb/hp-hr in notch 4, 5 & 6, a minimum of ~0.330lb/hp-hr in notch 7 and a bit higher in notch 8. Looks like you want to run in notch 7 or 8 as much as possible, idling some units when full power isn't needed. Would this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint? The complaint against Genset's was they took so long to fire up the additional HP and get it loading that the move had stalled by the time the additional power was available for use. I see that issue for gen-set use in switching applications. In road use where changes are less abrupt, and terrain is known this seems like it could be more automated and planned.
BaltACD rdamon Erik_Mag Paul Milenkovic What are these Notch 5 and 6 restrictions? I had seen data that diesel locomotives produce their best HP-hr/pound of fuel rates in Notch 8. A chart for the 16-710G3 shows ~ 0.405lb/hp-hr in notch 2, ~0.360lb/hp-hr in notch 3, just under 0.350lb/hp-hr in notch 4, 5 & 6, a minimum of ~0.330lb/hp-hr in notch 7 and a bit higher in notch 8. Looks like you want to run in notch 7 or 8 as much as possible, idling some units when full power isn't needed. Would this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint? The complaint against Genset's was they took so long to fire up the additional HP and get it loading that the move had stalled by the time the additional power was available for use.
The complaint against Genset's was they took so long to fire up the additional HP and get it loading that the move had stalled by the time the additional power was available for use.
My understanding - is that additional power is added when indicated by additional load being detected - I don't know if that additional load point can be tuned to various levels - up and/or down. I don't know if the operator has direct control of the additional power units on a Genset.
In the example of operating between Atlanta and Waycross over the rolling hills of Georgia - coming down the hills, I would expect that the GenSet operating algorithm would specify that 'additional power' wasn't needed and the order for additional power would not be created until the train was lugging down on the upgrade - eleminating the potential to use the kinetic energy of the downgrade to its best advantage.
Even before Carnegie-Mellon formalized the infrastructure and "IxD" requirements, it was clear that any 'road genset' design would have to follow previous-generation 'air pollution reduction' in being highly predictive of required load changes and then 'slowly enough' accelerating and then stabilizing prime-mover output speed and power. Note that Trip Optimizer and LEADER have the ability to track position and interrogate their proprietary interpretation of GIS to do this... with a little bit more careful programming.
The fun thing with the early select-a-power gensets was that idiots who recognized little if anything about practical switching seem to have set them up. It's almost as if the bureaucrats demonizing 'idling' in OTR trucks are mandating that the genset engines be shut down when 'not in use' -- the practical import being, for flat switching, that the additional power then involves both the latency in starting and warming the engine, followed by the slow anti pollution loading so familiar and loathed in generations of GE road power.
What is needed for flat switching is a button like that for an alerter, that a crew can 'whack' a predictable number of seconds before they make a joint or want to kick something. This takes the supplemental engine(s) up out of idle just in time to respond quickly to produce wheel torque. Note that dropping out of Ludicrous++ mode once accelerated to speed could be semi-automatic to conserve fuel and limit emissions.
This without any fancy energy storage for quick kicking, probably a good thing seeing what trouble generations of 'electric switch engines' from the Green Goat forward have with the current draw...
Note that the dramatic increase for lower notches was on an EMD two cycle engine, where the compressor is driven by the crankshaft at lower notches. A four cycle engine is likely to have a flatter sfc curve.
My impression is that a single large engine is more fuel efficient than several smaller engines of the same power.
I suspect the fuel economy should be looked at like a fan curve and system curve, with the fan curve being the locomotive(s) sfc and the system curve being train resistance as a function of speed. There must be a sweet spot where the locomotive sfc and train resistance combine to yield a minimum fuel consumption.
rdamonWould this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint?
One of the enabling things is the cheap, effective, and above all supported existence of small 'truck' engines that are Tier 4 supportable and designed for high operating efficiency. Were we still in an era where, say, Baldwin needed to design 412 or 408 engines from scratch and provide them in modules, the price still might be 'prohibitive' net of the economies and convenience to be gained.
There are two general effects of 'larger' Diesel engines. One is that thermal efficiency tends to increase with larger size and a couple of other parameters, notably longer stroke. Perhaps the most recognizable example is in large ship engines, with a multiplicity of pilot and main injectors, very long stroke, and thermally optimized materials and coatings. Until comparatively recently the idea of medium-speed engines in locomotives (maximum speed already getting into critical range for very strong construction for GEs in going to 1050 from 1000rpm) was vastly preferable to attempting the same effective shp from higher-speed engines (note that Progress, with every reason to flog the C175 family in locomotives, is staying with the 1010 'rebranding' of 275H technology in its competitive Tier 4 freight locomotives). Some of this is likely that combustion at slower speeds can have lower peak heat release and hence less nitrogen-oxide generation.
Meanwhile remember that about 70% of a diesel's power is involved in keeping itself running, and this is a major factor in increasing engine rpm (and hence developed power) when the engine is under load. If you have driven light diesel vehicles you have probably noted the improvement when you ease from a slightly higher speed into cruise instead of accelerating into it, even with torque-converter drive. The bigger engine consumes more fuel in accelerating itself, so operation in steady state is far more efficient providing you effectively use all the power so generated. This is one of the points of 'notch' vs. speed regulation, and (in passing) a reason you might want to restrict operating notch so as not to overspeed, or complicate slack action, in running at constant commanded rpm and using excitation combined with comparatively slow governed fuel increase at constant rpm for power change.
There are issues involved with displacement, too. Just as 'there is no substitute for cubic inches' in automobiles there are "mileage" consequences from larger displacement even net of cylinder interruption technology. Consequences of increased stroke (e.g. going from 429 to 460 in the Ford architecture) is lower fuel economy regardless of part load, and to the extent that effective 'turndown' on a large engine must be sufficient to keep it running but NOT (as on poorly-governed older Alcos) leaning it to the point of repeated stall followed by acceleration) the amount of fuel actually burned will be greater even if the sfc per mass of fuel is nominally better. (And, for the regulators, the mass of 'pollutant' release may be a separate topic from efficiency...)
Overmod rdamon Would this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint? A couple of considerations: One of the enabling things is the cheap, effective, and above all supported existence of small 'truck' engines that are Tier 4 supportable and designed for high operating efficiency. Were we still in an era where, say, Baldwin needed to design 412 or 408 engines from scratch and provide them in modules, the price still might be 'prohibitive' net of the economies and convenience to be gained. There are two general effects of 'larger' Diesel engines. One is that thermal efficiency tends to increase with larger size and a couple of other parameters, notably longer stroke. Perhaps the most recognizable example is in large ship engines, with a multiplicity of pilot and main injectors, very long stroke, and thermally optimized materials and coatings. Until comparatively recently the idea of medium-speed engines in locomotives (maximum speed already getting into critical range for very strong construction for GEs in going to 1050 from 1000rpm) was vastly preferable to attempting the same effective shp from higher-speed engines (note that Progress, with every reason to flog the C175 family in locomotives, is staying with the 1010 'rebranding' of 275H technology in its competitive Tier 4 freight locomotives). Some of this is likely that combustion at slower speeds can have lower peak heat release and hence less nitrogen-oxide generation. Meanwhile remember that about 70% of a diesel's power is involved in keeping itself running, and this is a major factor in increasing engine rpm (and hence developed power) when the engine is under load. If you have driven light diesel vehicles you have probably noted the improvement when you ease from a slightly higher speed into cruise instead of accelerating into it, even with torque-converter drive. The bigger engine consumes more fuel in accelerating itself, so operation in steady state is far more efficient providing you effectively use all the power so generated. This is one of the points of 'notch' vs. speed regulation, and (in passing) a reason you might want to restrict operating notch so as not to overspeed, or complicate slack action, in running at constant commanded rpm and using excitation combined with comparatively slow governed fuel increase at constant rpm for power change. There are issues involved with displacement, too. Just as 'there is no substitute for cubic inches' in automobiles there are "mileage" consequences from larger displacement even net of cylinder interruption technology. Consequences of increased stroke (e.g. going from 429 to 460 in the Ford architecture) is lower fuel economy regardless of part load, and to the extent that effective 'turndown' on a large engine must be sufficient to keep it running but NOT (as on poorly-governed older Alcos) leaning it to the point of repeated stall followed by acceleration) the amount of fuel actually burned will be greater even if the sfc per mass of fuel is nominally better. (And, for the regulators, the mass of 'pollutant' release may be a separate topic from efficiency...)
rdamon Would this say that a multiple unit gen-set design would be the most efficient for a fuel consumption and tractive effort standpoint?
A couple of considerations:
The GE Tier-IV units have clearance issues too.
M636c had a good story about the standard SD70ACe's and one of the iron ore dumpers in Australia.
Greetings from Alberta
-an Articulate Malcontent
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